Despite dissimilar underlying physiological and perceptual characteristics of ataxic and hypokinetic dysarthria, speaking rate control has been reported in the clinical literature to be a promising intervention technique in order to increase the intelligibility of these speakers. However, some clinicians report that rate control may disrupt the natural prosody of speech. The purpose of this project is to document the effects of various speaking rates and rate control strategies on the timing, intelligibility, prosody and articulatory precision of ataxic and hypokinetic dysarthic speech. Speaking rates will be controlled by a microcomputer which will be programmed to display a series of passages on a screen at various rates and analysis of audio recordings of eight ataxic dysarthric, eight hypokinetic dysarthric and 16 normal speakers: articulation time, pause time, voice fundamental frequency and intensity. Trained judges will listen to the audio tapes in order to measure intelligibility, stressing patterns and bizarreness. Specific research questions include the following: What adjustments in timing do dysarthric and normal speakers make as they reduce their speaking rate? What is impact of speaking rate and rate control strategy on intelligibility, prosody and articulatory precision? It is hoped that understanding the consequences of various rate control strategies would not only lead to better designed, more effective treatment programs but also add to our understanding of the perceptual physiological and zcoustic characteristics of certain types of dysarthria.